1. Field of the Invention
The present invention relates to an illumination apparatus and a projection display apparatus that use a red component light, a green component light, and a blue component light.
2. Description of the Related Art
Heretofore, there has been known a projection display apparatus that includes: three light valves corresponding respectively to light beams of three colors: a cross dichroic cube configured to combine light beams emitted from the three light valves; and projection means configured to project the light beams combined by the cross dichroic cube.
Here, the cross dichroic cube has: three light-incident surfaces on which light beams are incident; and a single light-emitting surface from which light beams are emitted. Accordingly, when light beams of three colors are to be incident on the cross dichroic cube, the projection display apparatus needs only a single cross dichroic cube.
Meanwhile, for the purpose of improving color reproducibility and brightness, there has been proposed a projection display apparatus using light beams of four or more colors. For example, the projection display apparatus has improved color reproducibility and brightness by using, for example, orange, yellow, or cyan in addition to three colors of red, green, and blue (for example, see Japanese Patent Application Publication No. 2002-287247 (claims 1 and 4, FIG. 1, and the like)).
In this respect, when the projection display apparatus has light beams of four or more colors, it is impossible to combine the light beams of four or more colors by only a single cross dichroic cube. For this reason, the projection display apparatus needs to include multiple dichroic cubes (or, cross dichroic cubes).
For example, assume a case where light beams of four colors need to be combined with one another. In this case, the projection display apparatus firstly obtains two combined light beams each by combining light beams of two colors, and further combines the two combined light beams with each other so as to obtain a combined light beam of four colors. It should be noted that the projection display apparatus may obtain a combined light beam of four colors by firstly obtaining a combined light beam of three colors, and then combining the combined light beam of three colors with a light beam of a single color. Alternatively, the projection display apparatus may obtain a combined light beam of four colors by firstly obtaining a combined light beam of two colors, and then combining the combined light beam of two colors with light beams of two colors.
In this regard, it is necessary that multiple dichroic cubes (or, cross dichroic cubes) be provided between the light valves and the projection means. For this reason, the back focus of the projection means is made long.
Consequently, the attempt to improve color reproducibility and brightness results in an increase in cost of the entire projection display apparatus because the projection means that is employed in the projection display apparatus using light beams of three colors cannot be utilized for such projection display apparatuses using four or more color light beams.